I think opening notes are useful, even if they are only a compilation of other sources. I organized mine MCO style with columns and footnotes. You can even put an assessment at the end of the column.
Writing down your possible opening moves?

I tried writing a move tree once, but I couldn't find paper that was big enough for it.
I started an idea i got from Awardness. When i am on the throne i us toilet tissue when i think of moves to play that involve several lines of play.

Now you can go to the dollar store and get those long yellow pads that are almost as long as your arm. Which can allow you to write 20 - 40 moves depending on how you write them for each line of thinking.

Well when school supplies are on sale stock up that should be at the end of summer and in the fall. I am sure you have some thrift store in Canada that will do at the moment till school starts and then hit the sales.

Chess Position Trainer lets you do exactly this by simply making the moves on the board. You can then train your memory using the spaced repetition theory using your chosen moves.

Yeah Bobby Fischer had a great memory.
His famous quote now they have so many examples they know what to do in these situations.

It's good to create an opening repertoire. Spend more time on analyzing variations that are played more often, and on ones that are more "exact". Don't build very deep variation lines, cease that as soon as you have a realtively equal position with Black or when you have some advantage and know how to further use it with White.
As MJ4H wrote, Chess Position Trainer is an excellent tool for repertoire building, analysis and training, try it and you'll most probably like it. It's good for storing variations and positions and training to play the repertoire. It doesn't include evaluation tools for the lines, in the sense it only stores moves and variations but doesn't give you advices. However you can write down your own evaluations for the positions. The interface is very good, has enough tools and is easy to use, and also it's free.
However you build your repertoire, you should have some way to store what you choose (be it on paper or a program), and look for information about the lines, probably from books / articles - engine evaluations are useful, but they are sometimes not accurate and they by themselves don't give you information how to play.
Good luck!

What's the point? Having a good memory is a part of being a good chess player. If you are referring to your notes during a game, then that is just another form of cheating.

That is why i keep it in between my ears where nobody can get to it but me. Locked deep inside my brain.

1- What does it do that a brain cannot do ?
2- It means you are tying yourself to a specific opening, which I would never do. Unless you rewrite the paper every month or so.

What's the point? Having a good memory is a part of being a good chess player. If you are referring to your notes during a game, then that is just another form of cheating.
Not in Correspondence Chess (online chess here). Live and OTB, yes. But the rules of CC (and, by extension, online) allow for notes to be kept and used.

What's the point? Having a good memory is a part of being a good chess player. If you are referring to your notes during a game, then that is just another form of cheating.
Not in Correspondence Chess (online chess here). Live and OTB, yes. But the rules of CC (and, by extension, online) allow for notes to be kept and used.
So, you have written down the main lines and variations of a specific opening. You refer to your notes during a game. How is that any different from using a chess engine during the opening?
The winner of a game of chess is usually the better player, and should not be the one with the best notes, best chess books, best chess engine etc, etc.
It's all cheating in my book, even if it is within the rules.
I have been thinking of writing in a paper what should be my next move according to what my opponent plays. So, for example, if I am playing black and my opponent plays e4, I will definitely play c6 (Caro-Kann). Then, if he plays d4 I will play d5, and there, he can play exd5 (exchange variation), e5 (advance variation) and Nc3 (standard, unorthodox replies). On exd5 I will respond with cxd5, on e5 I will play Bf5, and on Nc3 I will play dxe4, and I will keep doing the same thing until where I can reach. Sure there would be a lot of moves to write, but I think it would be very useful to have a good opening, what do you think?